Another Clarifying Question - Strakes and Wave Shield

AuthorizedUser

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Another question gang as I look to add a few items to my build. Reminder: 20SLG with 90hp dual toon. My dealer said it's pointless for me to add lifting strakes to the build with a 90hp dual toon (not elliptical). He says the motor is not big enough to really use the strakes and that they will only really help in turning... maybe. He said they won't do anything to make it more of a 'planing boat'... the dual logs will still plow through the water even with the strakes. Is he right?

BUT! He did strongly recommend the wave shield. While he couldn't guarantee any 'real performance enhancements' with it, he said there is nothing to not like about the shield... how it protects the bottom, keeps things covered. I mentioned less surging and a quieter deck and he agreed, but he did not mention those as benefits without my prompting.

So... yes or no for strakes? Yes or no for wave shield? Thanks!
 

DejaWiz

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Wave Shield will definitely offer a smoother ride, as it will vastly reduce or outright eliminate any surging from water hitting the crossbeams underneath.

Strakes...eh, a VF90 with the proper prop will likely be able to push a lighter 20' twin pontoon enough to get on plane at around 15-20 MPH (maybe even lower with a light load), but that'll come down to your personal preference and your wallet...if your primary usage is going to be slow to moderate speed cruising to a given spot, drop anchor, and relax then strakes may not be worth the cost. However, if you are wanting some faster and more efficient straight-line performance, then it may be worth it. Figure about 10% higher speed and less fuel consumption with strakes...it's going to take a long time to reach the break even point in small fuel savings for the strakes to eventually pay for themselves.


[EDIT]
Checking the Yamaha Performance Bulletins for 20-21' boats with two round pontoons and a 90HP, they top out between 25-30 MPH, which is fast enough for strakes to do their thing.

The most common props for the fastest of the bunch listed in the bulletins are:
Aluminum K-series 13-5/8 x 14
Talon SDS stainless 13-1/8 x 14
 
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Potomacbassin’

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Do I sense some PADS setting in? ;)

This is from an old Bennington manual (below).

The hull speed for a typical 20ft pontoon is probably somewhere in the 13-18 mph range, so if Bennington is stating 25mph with a 90HP then it is clearly planing (not plowing) and will definitely benefit from lifting strakes. But I think what your dealer may be trying to say, and echoed by Dejawiz - is that benefit worth the cost?

I tend to evaluate not only raw performance gains, but also situational advantages. For example, if I'm 20 miles from the marina and a pop-up thunderstorm shows up on the radar, can I get me and my kids home safely before the "s" hits the fan? Or if I'm making a long run to the city, can I make it on one tank of gas instead of having to fuel up and kill 30 minutes of our trip? Those small gains may not seem worth it on paper, but experiences over time may change that calculus.

Based on my needs, it would be yes to both. But based on your projected use and priority to stick close to budget probably no on the strakes and yes to the wave shield.
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BulldogsCadillac

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I would definitely do the underskinning! Couple reasons like mentioned previously (surging, rough water waves etc) but also because it protects the wood! Yes I know it is marine grade wood, but I know over the 10+ years I've been on here, every once and a while you hear of someone's carpet getting wet from underneath. Granted it shouldn't happen, but I'd rather take advantage of the other benefits and also ensure it doesn't happen. Water can do some crazy things when pushed / deflected.

As for the strakes, I don't honestly know if you would benefit, I didn't have them on my 2075 GLi with a 90hp, but I don't think it would have been an earth shattering speed increase if at all. I probably wouldn't bother, jmo
 

AuthorizedUser

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Do I sense some PADS setting in? ;)

This is from an old Bennington manual (below).

The hull speed for a typical 20ft pontoon is probably somewhere in the 13-18 mph range, so if Bennington is stating 25mph with a 90HP then it is clearly planing (not plowing) and will definitely benefit from lifting strakes. But I think what your dealer may be trying to say, and echoed by Dejawiz - is that benefit worth the cost?

I tend to evaluate not only raw performance gains, but also situational advantages. For example, if I'm 20 miles from the marina and a pop-up thunderstorm shows up on the radar, can I get me and my kids home safely before the "s" hits the fan? Or if I'm making a long run to the city, can I make it on one tank of gas instead of having to fuel up and kill 30 minutes of our trip? Those small gains may not seem worth it on paper, but experiences over time may change that calculus.

Based on my needs, it would be yes to both. But based on your projected use and priority to stick close to budget probably no on the strakes and yes to the wave shield.
View attachment 28139
No PADS, ever! I just want to make sure I can fully enjoy the boat I'm buying. I'm sold on the wave shield, will probably pass on the strakes.
 

sjhorner9475

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I agree with your dealer. Yes to the wave shield and no to the lifting strakes.
 

AuthorizedUser

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